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Wednesday, December 5, 2012

There have been multiple publications referenced here on using Neuromics' i-Fect siRNA Delivery Kit to study the effect of silencing genes known to play a role in Pain Signaling. These include: DOR,The β3 subunit of the Na+,K+-ATPase, NTS1, NAV1.8, TRPV1 NOV, β-arrestin, TRPV1, CAV1.2 and ASIC.

Highlights: Here, we report that the potassium channel subunit Kv9.1 is expressed in myelinated sensory neurons, but is absent from small unmyelinated neurons. Kv9.1 expression was strongly and rapidly downregulated following axotomy, with a time course that matches the development of spontaneous activity and pain hypersensitivity in animal models. Interestingly, siRNA-mediated knock-down of Kv9.1 in naive rats led to neuropathic pain behaviors. Diminished Kv9.1 function also augmented myelinated sensory neuron excitability, manifested as spontaneous firing, hyper-responsiveness to stimulation, and persistent after-discharge. Intracellular recordings from ex vivo dorsal root ganglion preparations revealed that Kv9.1 knock-down was linked to lowered firing thresholds and increased firing rates under physiologically relevant conditions of extracellular potassium accumulation during prolonged activity. Similar neurophysiological changes were detected in animals subjected to traumatic nerve injury and provide an explanation for neuropathic pain symptoms, including poorly understood conditions such as hyperpathia and paresthesias. In summary, our results demonstrate that Kv9.1 dysfunction leads to spontaneous and evoked neuronal hyperexcitability in myelinated fibers, coupled with development of neuropathic pain behaviors.

n vivo RNA interference: Anesthetized rats were subjected to a thoracic laminectomy and a silastic tube was inserted subdurally to lie just rostral to L3 DRG and externalized to deliver bolus injections (one injection per day for 4 consecutive days). Animals were allowed to recover for 5 d before treatment commenced. On the day of injection, siRNA was mixed with i-Fect (Neuromics) to a final concentration of 0.2 μg μl−1, according to published protocols (Luo et al., 2005). For each treatment, 10–20 μl of Kv9.1 siRNA or scrambled control mixture was injected, followed by a 10 μl saline flush. Twenty-four hours after the fourth injection animals were killed and L5 DRGs fresh dissected for qRT-PCR analysis. A separate set of animals were PFA perfused and DRGs retrieved for IHC. Passenger strand sequences for Kv9.1 and scrambled control siRNAs were cuuggaaucuguaggauca and gaggcctaatcgatatgtt, respectively (Dharmacon; “in vivo processing” option).